Continuously variable transmissions (CVTs) are used in many kinds of wheeled and tracked vehicles to transfer power from the engine to the wheels or tracks of the vehicle. A CVT has a driving pulley and a driven pulley connected by an endless belt. Each pulley has a pair of opposing sheaves, at least one of which is axially moveable, holding the belt between them. The opposing pulley sheaves exert a clamping force on the belt to keep the belt engaged so that the rotational motion of the driving pulley can be transmitted to the driven pulley. The diameters of the driving pulley and the driven pulley are in inverse relationship due to the relatively fixed length of the belt spanning the two pulleys. The belt moves up and down the opposing pulley sheaves as the diameter of the pulley changes. This clamping force exerted on the belt by the opposing pulley sheaves and the motion of the belt against the surface of the sheaves generates a significant amount of heat. The amount of heat generated can be a problem in vehicles used on rugged terrains or those carrying large amounts of load, such as all-terrain vehicles and the like, which encounter frequent changes of speed and/or output torque required to negotiate the rough terrain.
There is thus a need for a CVT assembly which provides adequate cooling to prevent wear and damage, especially to the belt, due to excessive heat.